As mobile communication becomes more and more global and new mobile generations become more common and the number of network operators providing mobile services increases, the need to share mobile network resources between several network operators has increased considerably. Mobile networks are shared e.g. when a group of network operators together receive a license for setting up a 3G mobile communication system but each of the network operators has its own infrastructure, which will at least partly be used as before. A shared mobile communication system thus comprises network elements that are jointly used by network operators and elements that are privately used by each network operator.
A network operator that does not belong to the above-mentioned network sharing system may utilize a shared mobile network by using a roaming service provided by such a shared mobile network.
A problem with the prior art solution is the routing of a call of a subscriber such that the routing takes place in a desired manner in the network elements managed by the network operators that participate in sharing the network. The routing of the call is based on a roaming number allocated to the call of a subscriber by a visitor location register of the visited mobile network, the allocation of the roaming number in the prior art solutions being based on the location area of the visited location register of the subscriber. The roaming number to be allocated according to the prior art cannot thus be used for routing a call in a shared mobile network.